Species diversity is unevenly distributed across the planet and among different kinds of organisms. We aim to understand the evolutionary processes that explain this variation, by disentangling the roles of speciation, extinction and competition in shaping present-day diversity patterns. A particular focus has been the evolutionary origins of latitudinal diversity gradients and of biodiversity hotspots such as the Cape floristic region of South Africa and the Indo-Pacific triangle. We also collaborate in initiatives reconstructing phylogenetic relationships in flowering plants and beetles.

Recent work has explored whether geographical isolation and lineage turnover – processes normally thought of as causing divergence at the species level – might cause the evolution of discrete units of diversity at levels above the species. We introduced the concept of higher evolutionarily significant units to define clades with diversity patterns shaped by shared evolutionary fate as well as evolutionary history. We have also demonstrated phylogenetic patterns consistent with these theories in mammals and plants.

The number of species of Protea found within 1 degree grid cells (Valente et al. 2010). Phylogenetic analyses show that the genus has diversified at the same net rate in the Cape biodiversity hotspot and in the rest of Africa, but at a much smaller spatial scale in the Cape.